Dual purpose feet for blindstitch machines



Aprifl 21; 1959 E. F. DUNN 2,832,350

' DUAL PURPOSE FEET FOR BLINDSTITCH'MACHINES Filed. June 4, 1957 2 Sheets-Sheet l INVENTOR.

' Earl F Dunn wmvsss I BY TTORNEY W E. F. DUNN 2,882,50

' DUAL PURPOSE FEET FOR BLINDSTITCH MACHINES Filed June 4, 1957 2 Sheets-Sheet 2 INVENTOR. Earl E Dunn WITNESS ATTO NEY United States Patent DUAL PURPOSE FEET FOR BLINDSTITCH IVLACHINES Earl F. Dunn, Bridgeport, Conn., assignor to The Singer Manufacturing Company, Elizabeth, N.J., a corporation of New Jersey Application June 4, 1957, Serial No. 663,410

Claims. (Cl. 112260) This invention relates to blindstitch sewing machines, and more particularly, to an improved work supporting mechanism for a blindstitch sewing machine.

It is an object of this invention to provide in a blindstitch sewing machine having a free ended work arm, a Work supporting mechanism adapted to accommodate uneven thicknesses of work fabric on opposite sides of the stitching point and to apply uniform pressure to the work fabric on each side of the stitching point.

It is also an object of this invention to provide a work support for a blindstitch sewing machine which at the will of the sewing machine operator may be made to apply either uniform pressure at each side of the stitching point or a different pressure on each side depending upon the difference in thickness of the work fabrics at each side of the stitching point.

Another object of this invention is to provide a work support of the above character which will facilitate insertion of a work fabric to the stitching point of the sewing machine.

With the above and other objects and advantages in view as will hereinafter appear, this invention comprises the devices, combinations, and arrangements of parts hereinafter described and illustrated in the accompanying drawings of a preferred embodiment in which:

Fig. 1 represents an end elevational view of a blindstitch sewing machine having this invention applied thereto;

Fig. 2 represents an enlarged end elevational view of the work arm and a fragment of the bracket arm, with the work arm and portions of the work supporting mechanism being in section;

Fig. 3 represents an enlarged top plan view of a portion of the work arm of Fig. 1 with the work supporting feet and the ridge former removed and the parts arranged in a position such that each of the work engaging feet will be urged upwardly with uniform pressure regardless of differences in work thickness at each side;

Fig. 4 represents an enlarged top plan view similar to that of Fig. 3 but in which the parts are arranged in a position such that each work engaging foot will be urged upwardly with a different pressure depending upon the thickness of the stitching point;

Fig. 5 is an enlarged cross sectional view taken substantially along line 55 of Fig. 3, and

Fig. 6 represents an enlarged cross sectional view of the work arm taken substantially along the line 6-6 of Fig. 1.

Referring more particularly to Fig. 1, this invention is applied to a blindstitch sewing machine having a conventional frame including a base 11, a work arm 12 pivotally supported, as at 13 on the base and extending transversely beneath the free extremity of a bracket arm 14. The work arm is preferably of the cantilevered or free ended type adapted to accommodate tubular or curved fabric sections.

Reference may be had to the. United States patent of ..Parry No. 2,718,862, September.

27, 1955, for a more complete disclosure of this type of free ended work arm in a blindstitch sewing machine.

A throat plate 15 is fixed on the bracket arm beneath which the work fabrics are directed during the sewing operation. Carried for oscillatory movement in the bracket arm above the throat plate is a curved needle 16 and an orbitally movable looper 17 adapted to cooperate with the needle in the formation of stitches. An oscillatory ridge former 18 is carried in the work arm and is adapted to force a ridge of fabric upwardly through an aperture 19 in the throat plate and into the path of the oscillating curved needle. As is conventional in this type of blindstitch sewing machine, the work arm 12 is biased upwardly by a spring (not shown) into an operative position as determined by a stop arm 20 journaled 0n the pivotal support 13 and anchored in the machine frame. The stop arm abuts the front skirt 21 of the work arm to limit the height of the operative position of the ridge former. 5

The bracket arm also carries a work feeding mechanism including a feed dog 22 which operates through the aperture 19 in the throat plate to engage and advance the fabrics in a direction to the left as viewed in Fig. l. The work supporting mechanism of this invention is carried in the work arm 12 and is arranged to oppose the feed dog 22 and also to maintain the work fabrics evenly at each side of the ridge former.

The work supporting mechanism comprises a pair of work supporting feet 23 and 24 pivotally secured, as by shouldered pivot screws 25 one to each of a pair of links 26 and 27. Each of the links with a work supporting foot secured thereto constitutes a presser unit, the units being disposed in side by side relation one at each side of the ridge former 18. The links 26 and 27 are journaled for turning movement on an elongated pivot pin 28 fast in the work arm and, as best illustrated in Fig. 2, the links extend substantially in the direction of action of the feed dog 22 from the pivot pin 28 beneath the ridge former to the pivot screws 25.

Also journaled on the elongate pivot pin 28 are a pair of arms 29 and 30 which, as best illustrated in Figs. 3 and 4, are disposed one on each side of the pair of links 26 and 27. Each of the arms 29 and 30 is biased upwardly by means of a coil spring 31 and 32 respectively, the coil springs being seated in threaded bores 33 in the work arm and cavities 34 formed beneath arms 29 and 30. Set screws 35 in the threaded work arm bores 33 abut the springs and serve as means to adjust effectiveness thereof in biasing the arms 29 and 30 upwardly. Each of the arms 29 and 30 is formed with a downwardly extending stop finger 36 disposed for engagement with set screws 37 threaded in the work arm serving to limit the maximum upward position of the frame arms 29 and 30 in response to the force of the coil springs 31 and 32.

By means of mechanism which Will now be described, the sewing machine operator may either lock the two arms 29 and 30 together at their free extremities to form a unitary U-shaped frame or separate the two arms for movement independently one with respect to the other. With reference to Figs. 3, 4 and 5, the arm 29 is formed at its free extremity with an inturned finger 38 which is provided with a threaded aperture 39 extending transversely of the pivot pin 28. Threaded into the aperture" 39 is a screw 40 formed on the extremity extending toward the pivot pin 28 with a straight cylindrical shank; portion 41 of reduced diameter which forms a shoulder 42 at its juncture with the threaded portion of the screw shank. As best illustrated in Fig. 5, a latch block 43 is loosely journaled on the straight cylindrical shank 41 of the screw 40 and confined thereon between the shoulder, 42 and an equalizing lever 44 formed with lever arms 44 and 44". The lever 44 is pivoted-on the freeextremity 6f the shank 41 and confined thereon by a shouldered fastening screw 45. Thela'tch block iywill'thus be shifted toward and away from the pivot pin 28 as the screw 40 is turned with respect to the inturned finger 38 of the arm 29. A tangor latch lug '46 which is formed on the side of the latch member which faces thear-m 30 cooperates with a slot 47 formed in the arm '30 to lock the two arms 29 and 31) together as aunit when the screw 40 is turned in a clockwise direction to shift the latch block 'toward'the :pivot .pin 28 and into a position as illustrated inFig. '3. When the screw 49 is'turned ina counterclockwise direction to the positionas illustrated in Fig. 4, the latch block will be shifted so as to' carry the tang "46 clear of the slot 4-7 thusseparating the arms'29 andil'd.

Eachbf the presser foot carrying links '27 and f26 :is formed with a downwardly extending abutment lng'48, 49 respectively, which lugs are adapted to hear one upon eacharm44' and d4" of the equalizing lever '44 onelug on each side of the cylindrical'shank 41 on ,whichthe equalizing lever is 'fulcrumed. When the screw 40 is turnedclockwise to the position illustrated in'Fig. 3, the equalizing lever will occupy a position beneath the .lugs 48 2111(149 and the ,presser feet will be interrelated by the equalizing lever such that thicker fabric between the throat plate and one of the presserfeet will merely cause the equalizing lever 44 to assume an angular position while the combined'force of the two coil springs '31 and 32'will act in concert, by way of the joined arms 29 and 30 to exert substantially equal force on each of the presser feet.

When the screw 40 is turned in a counterclockwise direction, the equalizing lever 44 will be carried along with the latch member '43 and will assume a position as illustrated in Fig. 4 out from beneath the downturned lugs 48 and 49 such that the presser feet will respond independently to thicker or thinner fabrics thereon.

A light coil spring 50 is anchored at one end in the arm 29 and extends at the other extremity through a hole formed in the equalizing lever 44. The springSO serves to urge the equalizing lever into the position illustrated in Fig. 6, that is, the position which the equalizing lever will occupy when arranged beneath the downturned lugs 48 and 49 and when equal thicknesses of work are being sewn at each side of the ridge former. The spring 50 is preferably so light that the effect of the spring is negligible insofar as concerns the interaction between the presser feet. The function of the spring, however, is to hold the equalizing lever in proper position while the lever is shifted out from beneath the downturned lugs 48 and 49' so that proper reengagement of the lever beneath the lugs can always be accomplished. When the equalizing lever is disposed beneath the lugs 48 and 49, an additional purpose is served'by the spring 50 inthat the work supporting feet will be thereby maintained at substantially equal elevations when the work arm 12 is lowered to facilitate removal or insertion of work fabrics in the sewing machine.

Thelatch member 43 is preferably formed with a finger 51-which extends laterally across the arm 29 and'then is bent into a hook shape such that its free extremity also extends laterally across the arm 29 in position to be shifted between the arm 29 and the presser foot support ing link 26. The finger 51 performs two functions, first it aids in preventing turning movement of the latch member on the cylindrical shank 41 so that the latch lug 46 will "always be positioned in register with the slot 47. Second, the finger S1 in being shifted forwardly with the latchmember 43 when the screw 40 is turned counterclockwise, will act between the arm 29 and the link 26 toelevate the link 26 slightly and thereby to provide a clearance between the downturned lug 48 and the equaliz'ing lever 44 so that the lever 44:may be repositioned beneath the lug 48 without interference when the screw 40 isagaiu turned clockwise.

The latch member 43 is also provided with a finger 52 extending laterally across'the arm 30. The fing'er'SZ is drilled and tapped at its free extremity to accommodate a shouldered pivot screw 53 on which is journaled a finger 54 of which the free extremity is bent inwardly and extends over the arm 30 in position to be shifted between the arm 30 and the presser foot carrying link 27. The pivoted finger '54 serves in thesame manner as the finger 51 in separating the lug '49 from the equalizing lever 44 as the lever is being withdrawn from beneath the lug so as to enable the lever to be repositioned beneath the lug without interference.

In the blindstitch sewing machine described above, the fixed throat plate 15 against which the work is sustained is carried by the bracket arm and the spring loaded work supporting feet 23 and '24 are carried by the work arm 12. While it might seem as though this arrangement is simply a reversal of the customary arrangement in a conventionalsewing machine, in which the fixed throat plate is carried by the work arm and the spring loaded'presser foot is carried by the bracket arm, one problem-which is presented in a blindstitch machine and particularly one employing a free ended work arm as in the above described construction, is that in spring biasing the work supporting feet upwardly because of the limited space available in the work arm, the same bearing surfaces are not available widely spaced in the direction of the line of action of the biasing force in the blindstitch-work arm as are readily available in the bracket arm of a conventional-sewing machine. Under these circumstances, the use of a single spring comparable to that ordinarily used to bias a presser foot downwardly is not satisfactory in a free arm blindstitch machine since Without objectionable enlargement of the work arm only a narrow bearing surface is available and a single spring arrangementwould be subject to binding and considerablewear.

In the present invention, the problem has been solved by the use of a pair of pivoted arms 29 and 30 preferably each biased upwardly by separate springs 31 and 32. Whether the arms are joined for movement as a unit, or separated for independent movement, therefore, the work supporting feet will be biased upwardlywithout canting or binding of the parts and without binding of the springs.

In the present invention merely turning of the screw 40 enables the operator to change the action of the Work supporting feet from that in which each foot exerts an equal pressure regardless of differences in work thickness thereon, to that in which each foot is biased-independently and will exert an upward force which increases as the thickness of the work increases.

Insertion of work fabric into the-machine is -also facilitated by the arrangement whereby the work supporting feet links 28 and 29 extend substantially in the direction of action of the feed dog .22. Since the work fabrics are customarily inserted into the machine in this same direction, that is from right to left as viewed in Figs. 1 and '2, the forces used to shift the fabrics to the stitching point will give rise to-very favorable components of force tending to lower the work supporting feet, thus heavier fabrics or fabric seams requiring a plurality of folds or thicknesses may be inserted easily to the stitching point.

Having thus set forth the nature of the'invention, what I claim herein is:

1. In a blindstitch sewing machine having a bracket arm, a free ended work arm extending transversely benea'th said bracket arm, and stitch forming instrumental ities carried entirely by said bracketarm, means supporting a work fabric beneath said bracket arm comprising, a pivot shaft secured in said work arm, a pair of arms journaled on said pivot shaft, separate spring means biasing eachof said pair'of arms outwardly from said work arm, apair of links journaled on said pivot shaft and disposedeach for engagement with a respective one of said p i iofarms, a pair of worksupportingfeet carried "one by each of said links, operator influenced means carried by one of said pair of arms and shiftable into a position in engagement with the other of said arms to lock said arms together for movement as a unit, an equalizing lever fulcrumed on one of said pair of arms, and operator influenced means for shifting said equalizing lever into and out of operative engagement with said pair of links.

2. In a blindstitch sewing machine having a bracket arm, a free ended work arm extending transversely beneath said bracket arm, and stitch forming instrumentalities carried entirely by said bracket arm, means supporting a work fabric beneath said bracket arm comprising, a pivot shaft secured in said work arm, a pair of arms journaled on said pivot shaft, separate spring means biasing each of said pair of arms outwardly from said work arm, a pair of links journaled on said pivot shaft and disposed each for engagement with a respective one of said pair of arms, a pair of work supporting feet carried one by each of said links, an equalizing lever fulcrumed on a first of said pair of arms and shiftably supported thereon for bodily movement into and out of operative engagement with said pair of links, interlock means supported on said first of said pair of arms for movement into and out of a position in engagement with the second of said pair of arms, and operator influenced means operatively connected to both said equalizing lever and said interlock means effective to shift simultaneously said equalizing lever into engagement with said pair of links and said interlock means into engagement with the second of said pair of arms.

3. In a blindstitch sewing machine having a bracket arm, a work arm extending beneath said bracket arm, and stitch forming instrument-alities carried entirely by said bracket arm, means supporting a work fabric beneath said bracket arm comprising, a pivot shaft carried in said work arm transversely beneath said bracket arm, a pair of arms journaled on said pivot shaft, separate spring means biasing each of said pair of arms outwardly from said work arm, a block slidably supported on a first of said pair of arms, a mating tang and slot formed on said block and on the second of said pair of arms, means effective at the will of the operator for shifting said block with respect to the first of said arms to effect selectively an integration or a separation of said pair of arms, an equalizing lever fulcrumed on the first of said pair of arms and supported thereon for bodily movement with said block, a pair of links journaled on said pivot shaft, each of said links being disposed to overlie a respective one of said pair of arms, a pair of work supporting feet carried one by each of said links, and an abutment formed on each of said links, said abutment being disposed for engagement with said equalizing lever one on each side of the fulcrum thereof when said block is shifted into a position integrating said pair of arms.

4. In a blindstitch sewing machine having a bracket arm, a work arm extending beneath said bracket arm, and stitch forming instrumentalities carried by said bracket arm, means supporting a Work fabric beneath said bracket arm comprising, a pivot shaft carried in said work arm horizontally beneath said bracket arm, a pair of substantially horizontally disposed arms journaled on said pivot shaft, separate spring means biasing each of said pair of arms upwardly from said work arm, a block slidably supported on a first of said pair of arms, a mating tang and slot formed on said block and on the second of said pair of arms, means effective at the will of the operator for shifting said block with respect to the first of said arms to effect selectively an integration or a separation of said pair of arms, an equalizing lever formed with a pair of lever arms extending one on each side of a fulcrum, means pivoting said lever at the fulcrum thereof on the first of said pair of arms and for bodily movement with said block, a pair of links journaled on said pivot shaft, each of said links being disposed to overlie a respective one of said pair of arms, a pair of work supporting feet carried one by each of said links, an abutment formed on each of said links and disposed for engagement each with a respective one of the lever arms of said equalizing lever when said block is shifted into a position integrating said pair of arms, and a spring anchored in said equalizing lever and in the first of said pair of arms, said spring being disposed to bias said equalizing lever into a position in which the lever arms thereof are maintained substantially horizontally when said equalizing lever is shifted out of engagement with said links.

5. In a blindstitch sewing machine having a bracket arm, a work arm extending beneath said bracket arm, and stitch forming instrumentalities carried entirely by said bracket arm, means supporting a work fabric beneath said bracket arm comprising, a pivot shaft carried in said work arm transversely beneath said bracket arm, a pair of arms journaled on said pivot shaft, separate spring means biasing each of said pair of arms outwardly from said work arm, a block slidably supported on a first of said pair of arms, a mating tang and a slot formed on said block and on the second of said pair of arms, means effective at the will of the operator for shifting said block with respect to the first of said arms to effect selectively an integration or a separation of said pair of arms, a pair of links journaled on said pivot shaft, at least a portion of each of said links being disposed to overlie a respective one of said pair of arms, a pair of work engaging feet carried one by each of said links, an abutment formed on each of said links extending downwardly between said pair of arms, an equalizing lever fulcrumed on the first of said pair of arms, and supported thereon for bodily movement with said block to a position in engagement beneath each of said link abutments when said block is shifted into a position integrating said pair of arms and out of engagement with said abutments when said block is shifted into a position separating said pair of arms, and a pair of fingers articulated one relative to the other and carried for bodily movement with said block, said fingers being formed each to overlie a respective one of said pair of arms and disposed each to occupy a position between a respective one of said pair of arms and that portion of said links overlying said pair of arms when said block is shifted into a position separating said pair of arms.

References Cited in the file of this patent UNITED STATES PATENTS 

